An ignitable gas generating material is used to provide inflation gas for inflating a vehicle occupant restraint such as an air bag. The gas generating material is prepared as a mixture of particles which together include the ingredients of the gas generating material. A solid body of gas generating material, known as a grain, is formed from the particle mixture.
A plurality of grains of gas generating material are contained in an air bag inflator. The inflator has an initiator which ignites the grains of gas generating material when the air bag is to be inflated. As the grains of gas generating material burn in the inflator, they rapidly generate a large volume of inflation gas. The inflation gas is directed outward from the inflator and into the air bag to inflate the air bag.
When the grains of gas generating material are ignited in the inflator, the brisance from the initiator may cause the grains to crack or break apart. As a result, the combustible surface areas of the grains are increased. The rate at which the combustion of the gas generating material proceeds, and consequently the rate at which the inflation gas is generated, is increased accordingly.